An Atlas 5 rocket sent the Air Force's X-37B mini-shuttle on its first repeat flight on Tuesday, kicking off a months-long classified mission reportedly aimed at testing advanced spy satellite sensors.
Despite earlier concerns about the weather at Cape Canaveral Air Force Station, the launch went off on time, just after 1 p.m. ET.
One-fourth the size of the real space shuttle, the X-37B has captured the imaginations of everyone from amateur satellite trackers to potential military rivals. The X-37B can orbit Earth for months, then re-enter the atmosphere and land autonomously.
Each of the first two X-37B missions ended with the mini-shuttle landing on a runway at Vandenberg Air Force Base in California. Two different X-37Bs were flown for those missions, but this marks the first time that the 29-foot-long, Boeing-built craft has been reflown in space. The X-37B's reusability is one of its big selling points.
Although the Air Force has not publicly discussed what the space plane will be doing, experts have surmised that the sensors tested by the X-37B will be used on smaller satellites, including low-cost, 4-inch-wide (10-centimeter-wide) CubeSats that can be tracked from the field using little more than a laptop.
The Air Force says there's a chance this mission will end with a landing on the space shuttle runway here at Florida's Kennedy Space Center.